[PATCH net-next] tcp: fix tcp_send_syn_data()

[Eric Dumazet]

From: Eric Dumazet <eduma...@google.com>

syn_data was allocated by sk_stream_alloc_skb(), meaning
its destructor and _skb_refdst fields are mangled.

We need to call tcp_skb_tsorted_anchor_cleanup() before
calling kfree_skb() or kernel crashes.

Bug was reported by syzkaller bot.

Fixes: e2080072ed2d ("tcp: new list for sent but unacked skbs for RACK 
recovery")
Signed-off-by: Eric Dumazet <eduma...@google.com>
Reported-by: Dmitry Vyukov <dvyu...@google.com>
---
 net/ipv4/tcp_output.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 
53dc1267c85e668d9a6d5d60d24e6101f7a9c56b..988733f289c8c43f3ed88a9ae1b7f272ab8de1a2
 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3383,6 +3383,7 @@ static int tcp_send_syn_data(struct sock *sk, struct 
sk_buff *syn)
                int copied = copy_from_iter(skb_put(syn_data, space), space,
                                            &fo->data->msg_iter);
                if (unlikely(!copied)) {
+                       tcp_skb_tsorted_anchor_cleanup(syn_data);
                        kfree_skb(syn_data);
                        goto fallback;
                }